Rate gyroscope with torsional suspension



July 23, 1957 w. P. LEAR ET m.

RATE GYROSCOPE wrm TORSIONAL SUSPENSION Filed Oct. 25, 1951 I INVENTORS.

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2,800,024 Patented July 23, 1957 fifice RATE GYROSCOPE WITH TORSIONALSUSPENSION William P. Lear, Santa Monica, Calif., and Thomas 'Barish,Cleveland, Ohio, assignors to Lear, Incorporated, Grand Rapids, Mich acorporation of Illinois Application October 23, 1951, Serial No. 252,736

8 Claims. (Ci. 74-5} This invention relates to a mounting for agyroscope gimbal. More specifically it has relation to a gyroscope inwhich one or more of the gimbals is restricted in the amount of'a'ngulardisplacement on its axis.

An example of a gyroscope with which the invention may be incorporatedis the so-called rate gyroscope utilized in aerial navigation andcooperable with a vertical gyroscope in a manner to be explained. Whenutilizing an automatic pilot which depends upon a single verticalgyroscope for translating errors in pitch and roll into a voltageforming an input signal to the amplifiers driving thesurface-controlling servomotors the vertical gyroscope is, in mostmodern instruments, maintained to true vertical by means of agravity-responsive electrolytic switch. Such switch contains a pluralityof contacts and an electrically conductive fluid defining with theswitch casing a bubble. The circuit controlled through the contacts isenergized or deenergized in accordance with the position of the bubble.For a typical switch of this character reference may be had to U. S.Letters Patent No. 2,720,569, granted October 11, 1955, to John F.Schoeppel et al. The circuit, including the electrolytic switch, isconnected to a source of power and to torque motors arranged to maintainthe gyro to the reference vertical by driving the gimbals thereof.

When going into a turn it becomes necessary to eliminate erection of thegyroscope insofar as concerns the roll axis of the airplane, forotherwise the gyroscope will be erected to an apparent vertical, whichis no longer in the vertical fore and aft plane of the aircraft and, bysuch erection to an apparent vertical, false indications will result.

In order to open the circuit from those contacts of the electrolyticswitch which control erection in the roll sense a so-called rategyroscope is often employed. This instrument comprises a housingcontaining the gyroscope rotor, the housing being rotatably supported ona frame secured to the aircraft in such position that the gyroscope willsense the centrifugal force corresponding to a given rate of turn towhich the aircraft is then subjected and, by means of a suitable pickotfincorporated between the housing and the frame, will provide a signalwhich contains a rate component of such magnitude and phase as to effectopening of the roll erection circuit.

However the rate gyroscope should not be suspended so freely as to senseall random displacements of the airplane on its roll axis, since underthose circumstances the gyroscope will be effective to open and closethe roll erection circuit in compliance with every such displacement andthereby result in erratic performance of the autopilot system. On theother hand a sustained displacement above a minimum predetermined normand occurring about the roll axis, as would be the case in a turn,should be effective to cut out roll erection during the turn, and tore-establish the circuit upon resumption of level flight.

Accordingly we have found that the system for suspending the singlegimbal, i. e. housing, of the rate gyroscope must possess a degree ofrigidity which will render the gimbal relatively unresponsive to'minorfluctuations of the aircraft on its roll axis, but will allow a sensibledisplacement for such rate of turn 'as would cause false erection of thegyroscope and accordingly result in disabling the roll erectioncircuity.

In view of the foregoing a principal object of our invention is toprovide in a rate gyroscope semi-rigid means for mounting the rotorgimbal for permitting a limited degree of angular displacement'thereof.

Another object is to provide a pair of semi-rigid mountings for thegimbal of a gyroscope and an electrical pickoff at one end of thegimbal, the mounting at the pickoff end being substantially more rigidthan that at the opposite end.

A furtherobject is to provide mounting means as aforesaid which includesa torsionally deformable element.

Still a further object is to provide means as aforesaid which isadaptable to mounting a gimbal within a gimbal, with or withoutpickofr's associated with either gimbal.

Another object resides in providing torsionally bidirectionallydeformable elements as the rotational support for a gyroscope gimbal, inorder that movement of the gimbal on its axis may occur in either senseagainst the same amount of resilient opposing force.

Still another object is to provide a semi-rigid mounting for the gimbalof a gyroscope which, while permitting proper displacement of the gimbalin response to change in attitude of the craft, provides suitableprotection against misadjustment in the'pickofif due to shock.

7 Other objects will appear from the following description, taken withthe appended drawing, in which latter:

Fig. 1 shows a top plan view of a rate gyroscope embodying theinvention; I

Fig. 2 shows a front elevational view thereof, and partly sectioned;

Fig. 3 shows a right side-elevational view thereof;

Fig. 4 shows a somewhat magnified detail of the adjusting means for thearmature of the pickoif;

Fig. 5 shows an enlarged detail of one of the torsionally deformablemounting members;

Fig. 6 is a perspective view in detail of an alternative form of supportmember;

Fig. 7 is a cross-section taken on the line 77 of Fig. 6;

Fig. 8 is a diagrammatic representation showing an embodiment of theinvention in a gyroscope having more than one gimbal; and

Fig. 9 is a diagrammatic showing of a further modification of theinvention.

Broadly considered the invention improvement contemplates the securementintermediate the fixed framework of the instrument and the rotorhousing, i. e. gimbal, of an element which possesses a predeterminedtorsional resiliency but no perceptible longitudinal deflection underthe loads encountered and which element serves as one of the supportingmembers of the gimbal. Preferably the supporting members, if more thanone is employed, are of similar construction, and include a neckedportion so designed as to permit limited torsional deformation of themember about an axis corresponding to what may be termed the principalrotational axis of the gimbal, such axis lying in a plane including theaxis of the rotor and perpendicular to said latter axis. However lateraldeflection of the support member is maintained at an absolute minimumconsistent with the desired torsional characteristic, thus providingradial support for the gimbal and the elements carried thereby. Whenutilizing an E-I pickoff for translating the angular displacement of thegyroscope into an electrical signal having a magnitude and phasecorresponding to the magnitude and i must be kept as small as possible.

lem becomes one of providing a support member which .is comparativelyshort in its active portion, while possessed of that degree of torsionaldeformability'which will provide a suflicient Output signal from thepickoff.

direction of the angular displacement it has been found preferable toprovide that the supporting member adjacent the pickoif be stifler thanthe opposite member. In this way the possibility of disturbing theinitial, critical adjustment of the pickofi is materially reduced;

In another aspect the invention contemplates securement of thesupporting members to the frame by means of a clamping arrangement soconstructed that by tigh tening or loosening a clamping screw'micrometric angular .displacement of the supporting member may beeffected,

and the null position of the pickof't' rapidly and accurately achieved.1 i

As an alternative it is within contemplation to provide a torsionallyresilient but laterally rigid support mem- .ber which includes aplurality of similarly functioning placement in any direction which isnot tantamount to rotation about the axis of the supporting members,since such displacement is without significance in connection with agyroscope having only one degree of freedom,

and may provide spurious indications by precessive eflects.

However, in this connection it is not intended to limit the scope of theinvention to one-gimbal instruments, since l This construction ischaracterized by relatively higher rethe same are capable of beingembodied in gimbal mountings generally. And, when we use the phrasetorsionally deformable, We intend to refer to a member which possesses apredetermined capacity to be twisted about its longitudinal axis, andincorporating suflicient elasticity to be self-restoring to an initialposition. It will beunderstood that the design is such that under allworking conditions of the instrument the elastic limit of the materialis not exceeded. a

Referring to the drawings a gimbal in the form of a housing 10 isprovided with'bearings 11-11 for supporting the rotor 12 of thegyroscope. In the chosen example the rotor is arranged as the armatureof an electirc motor, the stator being indicated at 14. It will beundertsood that other motive means may be employed, e, g. compressedair. V a a For supporting the gimbal 10 on the baseor framework 15 thereis provided a pair of laterally rigid but torsionally deformable members17 and 18 (see Fig. 5), each comprising an enlarged portion 21,preferably cylindrical, and

hereinafter referred to as the support flange, a narrowed portion 22 and23, referred to as the neck, and a head 24, also preferably cylindrical.

Each flange 21 is press-fitted into a in each side of the housing, thesebeing the same and disposed at each end of an axis intersecting the axisof the rotor 12 and perpendicular thereto. Each head 24 (Fig. 4) isrigidly clamped by means of a bar'27 and suitable recess 25 screws 28-28 to a post 29 upstanding from the frame- W Work 15, and regardingwhich further elucidation will be movements of the gimbal, the gimbalsupports may be made sufficiently rigid as to have a naturalfrequency ofvibration well above those frequencies which are likely to beencountered. Furthermore'the bending; deflection Accordingly the prob-Another feature of importance is the provision of a support member atthat side of the gimbal nearest the pickoff which is substantially morerigid than the opposite member. Then, if the framework flexes under thestresses to which it may be subjected, either as a result of mishandlingor deformation of the surface to which the framework is secured, or as aresult of temperature changes, the possibility of disturbing the pre-setadjustment of the pickoif is considerably minimized.

Accordingly assuming a gyroscope having an angular momentum of say1,590,000 grams/cmP/sec. and a member of chrome-vanadium steel, SAE6150, the length A of the straight portion of the neck 22 may be on theorder of 0.120" for bothparts 17 and 18, whereas the diameter B of theneck may be on the order of 0.0413 and 0.043" respectively, therebyproviding a stiffer spring factor at the pickofi end of the gimbal.

Additionally the support members of' the invention exert a centeringaction upon the gimbal, i. e. any influence tending to displace thegimbal in a lateral sense is counteracted by the spring action. Howeverto .pro-

vide such response the spring cannot be too long. For a gyroscope havingthe general characteristics noted a spring as specified has been foundcapable of supplying not only ;the required torsional resiliency butalso the lateral recovery.

Alternatively it is within contemplation to provide a spring which is inmultiple, e. g. as shown in Figs. 6 and 7.

. verting the angular displacement ofthe gyroscope into a controllingimpulse, we prefer to utilize an E-I pickoff comprising an armature 31carried on a bracket 30 attached to the housing 10, and a stator 32including the windings 33, 34 and 35. Inasmuch as the principles'ofoperation of a pickoif of this type are Well known, no elaborationthereof will be set forth beyond stating that angular movement of thearmature is eifective'to vary the magnitude of the flux threading thecore at a rate depending upon the angular velocity of displacement ofthe gimbal. And, depending upon whether rotation of the armature isclockwise or counterclockwise, the output will be greater from one ofthe coils 33 or 35 than from the other. 1

By proper choice of flux density the gap between the armature and thepole pieces of the stator may be made extremely small, and the responseof the pickoif made almost exactly linear with respect to the anglethrough which the gimbal is rotated, i. e. for small angles ofdisplacement sinfl fl. To attain this requirement, and to provide equaloutput for both sides of the pickofl requires careful setting of thegap' at each side of the pickoff and means are therefore provided formicrometn'c adjustment of the armature.

. Turning to Fig. 4 it will be seen that while one side of the clampingblock 27 is abutted with the post 29, the other side is spaced awaytherefrom, as indicated at 36. Consequently upon tightening the screw 28individual 'to the gap 36 the head 24 may be rotated a minute amount, e.g. as shown by angle C, to effect adjustment of the gaps of the pickofl.Such result is made possible byfabricating the post 29 of material whichis penetrable .by' the head 24, so that in effect the latter is forcedinto the post. It will be understood that provision is made for coarseadjustment of the gaps, e. g. by means .of the screws by which thebracket 30 is attached by axial movement of the coils, or otherwise, andthat the fine adjustment described in connection with Fig. 4 is of amicrometric nature only.

From the foregoing it will have been comprehended that the invention isnot to be regarded as limited to the support of the single gimbal, i. e.housing, of a rate gyroscope of its frame, but is capable of beingembodied in the mounting of one gimbal upon another, e. g. as shown inFig. 8, in which a gimbal ring 41 upon which the rotor 42 is carried is,in turn, supported on another gimbal ring 43. The supports 4444 betweenthe two gimbals and the supports 4545 between the ring 43 and theframework 46 are constructed in accordance with the principles of theinvention, i. e. characterized by torsional deformability in thedirection of angular movement and stiffness in the direction of lateraldisplacement. Moreover if it is desired to incorporate the fundamentalsof the invention in an instrument for sensing the forces and hence therate of angular displacement about two axes simultaneously theembodiment of Fig. 9 may be resorted to. In this figure the rotor 52 issupported in a housing or gimbal 53, here illustrated for convenience asspherical, and the latter is semirigidly carried on torsionallydeformable members 5454 and 55-55. In order that rate of angulardisplacement may be sensed simultaneously about two axes the respectiveprincipal axes of the members are positioned in the same plane, and thatplane may correspond to the midplane transverse to the rotor axis.However torsional deformability of one pair, e. g. 55-55 must correspondto lateral deflection of the other pair 5454, and vice versa. Hencemembers in the form of flat plates are preferred, and are arranged inintedigitated pairs as shown, the respective ends of the cooperativepairs being secured to the gimbal or fixed framework as the case may be.Thus torsional action about a selected axis is accompanied by lateralrigidity, regardless of the pair of supports then in action.

While we have shown particular embodiments of our invention, it will beunderstood, of course, that we do not wish to be limited thereto sincemany modifications may be made, and we therefore contemplate by theappended claims to cover any such modifications as fall within the truespirit and scope of our invention.

Having thus described our invention, what we claim and desire to secureby Letters Patent is:

l. A gyroscope comprising a framework, a gimbal, a rotor mounted in saidgimbal, means for rotating said rotor, and means for supporting saidgimbal on said framework, including a pair of primarily torsionallydeformable axially aligned rods respectively secured at their endsbetween said gimbal and framework at opposite sides thereof, said rodspossessing the same degree of lateral deformability but differentdegrees of torsional deformability.

2. A gyroscope in accordance with claim 1 further characterized by anelectrical pickolf, including a fixed part and a movable part, themovable part of the pickoff being secured to one side of the gimbal andthe fixed part thereof being secured to the framework, the stiffer oneof the said rods being positioned adjacent said one side of the gimbal.

3. A gyroscope comprising a framework, a gimbal, a rotor mounted in saidgimbal, means for rotating said rotor, and means for supporting saidgimbal for limited angular displacement about an axis perpendicular tothe axis of the rotor comprising a pair of coaxial members positioned atopposite sides of the gimbal, each said member having an enlargement atone end and a shank at the other, said gimbal having means for clampingsaid enlargement and said framework having means for clamping saidshank, said members having a portion of reduced transverse cross sectionintermediate said enlargement and shank which is torsionally deformablein a predetermined degree depending upon the torque applied to displacethe housing about the axis of said members, said enlargement providingportions for adapting said reduced portions to a clamping type ofmounting of practical proportions.

4. A gyroscope in accordance with claim 3 in which the reduced portionof one member is of less transverse area than the other but the physicalcharacteristics of both members are otherwise essentially the same.

5. A gyroscope having a rotor, a gimbal upon which said rotor is carriedfor rotation, a framework, and a pair of members, one disposed at eachend of a common axis upon which said gimbal is adapted to rotate, eachmember comprising a plurality of parallelly disposed torsionallydeformable elements of quadrantal transverse cross-section, the springconstant of one of said members being greater than the other, andelectrical pickolf means adjacent that end thereof with which the memberhaving the greater spring constant is associated, the movable portion ofthe pickofi being carried on the gimbal and the fixed portion thereofbeing mounted on the framework.

5. A gyroscope comprising a framework, a housing, a rotor supported forrotation in said housing, means for rotating said rotor, means forsupporting said housing on said framework in a semi-rigid mannerincluding a pair of axially aligned, torsionally deformable memberssecured between the housing and framework, one of said members having agreater spring constant than the other, and a pickotf adjacent saidmember of greater spring constant for translating angular displacementof the housing into an electrical signal, one element of the pickofibeing secured to said housing, and the other element thereof beingsecured to said framework.

7. A gyroscope comprising a framework, a gimbal, a rotor supported forrotation in said gimbal, means for rotating said rotor, means forsupporting said gimbal on said framework in a semi-rigid manner,including a pair of members having a common axis perpendicular to theaxis of the rotor, said members being torsionally deformable about theiraxis but essentially laterally nondeformable, the torsional springconstant of one of said members being greater than that of the other.

8. A gyroscope comprising a frame, a rotor, a gimbal upon which saidrotor is carried for rotation, a pair of members upon which said gimbalis supported upon an axis for limited angular movement, each said memberincluding a support flange at one end thereof and a head at the otherend thereof and a plurality of torsionally deformable, substantiallyaxially extending, elongated elements therebetween, and means forsecuring said flange and head to said gimbal and frame respectively andon each side of said gimbal for support thereof.

References Cited in the file of this patent UNITED STATES PATENTS2,409,178 Allison Oct. 15, 1946 2,484,823 Hammond Oct. 18, 19492,511,178 Roters June 13, 1950 2,606,447 Boltinghouse Aug. 12, 1952FOREIGN PATENTS 200,833 Great Britain Oct. 4, 1923

